Vane for an aircraft turbomachine

ABSTRACT

A rotor vane for an aircraft turbine engine, the vane having an axis of rotation once it has been rigidly connected to a rotor and a stacking axis. The vane includes a blade extending between an internal platform and an external platform bearing at least one projecting lip. The external platform is configured to cooperate in a form-fitting manner with the complementary side edges of adjacent vanes. The rotor vane has wear-resistant covering of a lower side edge which extends over one wall of a substantially rectilinear first ridge of the platform and over one wall of a second ridge of the platform. The second ridge extends at least partially inside the lip and is inclined relative to the first ridge in a direction substantially parallel to a transverse axis of the lip.

TECHNICAL FIELD

The present invention relates to the general field of the manufacture ofrotor vanes for an aircraft turbomachine.

BACKGROUND

The prior art comprises in particular document FR-A1-2 985 759.

Typically, an axial turbine in a turbomachine consists of a series ofaxial stages (along the axis of circulation of the gas flow) arranged inseries. Each stage comprises a movable wheel with vane forming a rotorand a bladed distributor forming a stator. The movable wheel is rotatedopposite the corresponding distributor.

In this patent application, the upstream and downstream are defined inrelation to the normal flow direction of the air flows (upstream todownstream) through the turbomachine. The axis of rotation of the mainrotor of the turbomachine is referred to as the “axis of theturbomachine”. The axial direction is the direction of the axis of theturbomachine, and a radial direction is a direction perpendicular to theaxis of the turbomachine and intersecting this axis. Similarly, an axialplane is a plane containing the axis of the turbomachine, and a radialplane is a plane perpendicular to this axis. The adjectives “internal”and “external” are used with reference to a radial direction so that theinternal part of an element is, in a radial direction, closer to theaxis of the turbomachine than the external part of the same element. Thestacking axis of a vane is the axis perpendicular to the axis of theturbomachine, which passes through the centre of gravity of theinnermost section of the blade of the vane (i.e. the section closest tothe axis of the turbomachine). Typically, a turbomachine vane comprisesa blade extending along the stacking axis of the vane, between theproximal and distal (i.e., internal and external) ends of the vane.

The movable wheel conventionally consists of an annular disc centered onthe axis of rotation of the wheel to which a plurality of vanes areattached.

An example of a vane is shown in FIG. 1 . A vane of this type isdescribed in patent FR-B1-2 985 759. A schematically represented rotorwheel (60) and a disc (62) are shown in FIG. 1 . A schematicallyrepresented aircraft turbomachine (64) is also shown in FIG. 1 . Thisvane 10 comprises a blade 16 extending along the stacking axis X of thevane, between the proximal end 10A and distal end 10B of the vane 10. Atits proximal end 10A, the vane comprises a platform 19 and a root 12 bywhich it is attached to the disc (not shown). At its distal end 10B, thevane 10 has a heel 14. When several vanes 10 are fixed to the disc,their heels 14 are arranged edge to edge so as to form a circumferentialring delimiting a surface of revolution around the axis A of rotation ofthe wheel. The function of this ring is, in particular, to delimit theexternal surface of the stream duct of the gas flows circulating betweenthe blades 16 and to limit gas leaks at the distal end 10B of the vanes10.

The heel 14 comprises a platform 20 externally delimiting the streamduct of the gas circulating between the blades 16, and having oppositelateral edges 21, 22. The platform 20 comprises an upstream part 24called the “upstream spoiler” and a downstream part 28 called the“downstream spoiler”. The heel 14 also comprises upstream 31 anddownstream 32 sealing lips extending radially towards the outside fromthe external face of the platform 20. This lips have a generalcircumferential or transverse orientation with respect to the axis ofrotation of the wheel. Each of the lateral edges 21, 22 of the platformhas, between the upstream 31 and the downstream 32 lips, a profilesubstantially in “Z”.

When several vanes 10 are fixed on the disc, the upstream 31 anddownstream 32 lips are arranged edge to edge so as to form a rotatingring of axis A, this ring being contained substantially in a radialplane. One of the functions of such a ring is to limit the clearanceexisting between the vanes 10 and a casing (not shown) which surroundsthe vanes 10 in order to limit the gas leakage at this point. Thiscasing carries an abradable annular covering which can cooperate byfriction with the lips of the vanes in order to limit these leaks bylabyrinth effect.

In order to dampen the vibrations to which the vanes 10 are subjectedduring operation, the vanes 10 are mounted on their disc with atorsional stress around their stacking axis X. The geometry of the heels14 is such that each vane 10 is placed under torsional stress by bearingon the neighbouring vanes 10 mainly along lateral faces 34 of theupstream lip 31, within the framework of the vane geometry shown. Thelateral faces 34 thus define the inter-vanes contact surfaces and arethe site of high friction during operation of the turbomachine. In orderto be protected against wear, the lateral faces 34 are provided with acovering or insert of friction-resistant material. This can, forexample, be a material marketed under the brand name Stellite®. Thiswear-resistant covering 36 is best seen in FIG. 2 .

Typically, this wear-resistant covering 36 is applied to the lateralfaces 34 by welding, e.g. drop welding, which involves the creation ofan electric arc to melt the material. This is often a manual operation,the Stellite® type alloy being in the form of a liquid drop duringdeposition.

The Stellite® alloy is a steel alloy with a high content in chromium(Cr) and cobalt (Co). It may also contain a small amount of tungsten (W)or molybdenum (Mo) and a small amount of carbon (C). The Stellite® alloyis not forgeable and must be either cast or welded to an object of whichit forms part or into which it is inserted.

Cracks have been observed to develop after the drop of Stellite® hasbeen deposited on vanes, resulting in the scrapping of the vanes.

The present invention offers a simple, effective and economical solutionto this problem.

SUMMARY OF THE INVENTION

The present invention provides a rotor vane for an aircraftturbomachine, this vane having an axis of rotation once it has beenrigidly connected to a rotor and a stacking axis and comprising a bladeextending between an internal platform and an external platform bearingat least one projecting lip, said blade comprising a pressure side andan suction side and said external platform comprising pressure side andsuction side lateral edges, located on the side of said pressure sideand suction side respectively, and configured to cooperate in aform-fitting manner, and in particular by interlocking, withcomplementary lateral edges of adjacent vanes, each of said lateraledges comprising a wear-resistant covering, characterized in that thewear-resistant covering of the lateral edge located on the side of saidpressure side extends over one wall of a substantially rectilinear firstridge of the platform, and over one wall of a second ridge of theplatform, which extends at least partially in said lip and which isinclined with respect to said first ridge in a direction substantiallyparallel to a transverse axis of elongation of the lip.

The wear-resistant covering is thus deposited on ridges which stiffenthe vane and limit the risk of cracks appearing during this deposition.These ridges make it possible to thicken the areas where thewear-resistant covering is applied as required, thus ensuring betterheat dissipation during the deposition process and thus reducing therisk of crack formation.

In addition, the shape of the ridges is adapted on the one hand to limittheir size and that of the covering, and on the other hand to preventthe latter from contacting with the aforementioned abradable coveringextending around the wheel and in which the lips of the heel areintended to form annular grooves during operation. In the event that thelips are inclined with respect to a plane perpendicular to the axis ofrotation of the wheel, and the ridges of each vane are aligned (andtherefore not inclined with respect to each other), the second ridge mayoverflow beyond the lip and generate unwanted contact with the abradablecovering, resulting in a widening of the corresponding groove and a riskof increased gas leakage in this area.

The vane according to the invention may comprise one or more of thefollowing characteristics, taken in isolation from each other or incombination with each other:

-   -   said first ridge has a substantially constant thickness E1,    -   said second ridge has a thickness E2 less than E1,    -   the wear-resistant covering of the lateral edge located on the        side of said suction side extends over a wall of a third ridge,        this third ridge having a thickness E3 similar to E1,    -   each ridge thickness is measured in a direction substantially        perpendicular to a surface forming the ridge, or in a direction        substantially perpendicular to a longitudinal median plane or an        axis of elongation of the corresponding ridge,    -   said wall of said second ridge extends over 20-50% of the height        of the lip in which it extends, measured along the stacking        axis,    -   said lip comprises two opposite longitudinal ends, one of which        comprises at least partially said wall of said second ridge, and        the other of which comprises an extra thickness in a direction        perpendicular to said axis of elongation,    -   said lip is inclined with respect to a plane perpendicular to        said axis of rotation,    -   the vane comprises two protruding lips and said first ridge is        located between these lips, and    -   said second ridge has a first end connected to one end of said        first ridge and a second free end located at said pressure side        lateral edge.

The present invention further relates to a rotor wheel for an aircraftturbomachine, comprising a disc carrying on its periphery an annular rowof vanes as described above.

The present invention also concerns an aircraft turbomachine, comprisingat least one vane or wheel as described above.

BRIEF DESCRIPTION OF THE FIGURES

The invention will be better understood and other details, features andadvantages of the invention will appear more clearly when reading thefollowing description made by way of non-limitative example and withreference to the appended drawings in which:

FIG. 1 is a schematic perspective view of a turbine wheel vane for anaircraft turbomachine,

FIG. 2 is a larger scale schematic view of a part of another turbinewheel vane for an aircraft turbomachine,

FIG. 3 is a schematic side view of a rotor vane according to theinvention,

FIG. 4 is a schematic top view of the vane of FIG. 3 ,

FIGS. 5 and 6 are detail views of FIG. 4 , with FIG. 6 illustrating oneof the characteristics of the invention as opposed to FIG. 5 whichtherefore does not illustrate the invention, and

FIG. 7 is a schematic top view of the vane of FIG. 3 , in a crosssection view.

DETAILED DESCRIPTION OF AN EMBODIMENT

The invention applies to a movable wheel vane 10 as described above withreference to FIGS. 1 and 2 .

The vane 10 comprises at least one blade 16 which extends between twoplatforms, respectively internal 19 and external 20. The internalplatform 19 is connected to the radially internal end of the blade andthe external platform 20 is connected to the radially external end ofthe blade and comprises coverings 36 of wear-resistant material.

FIGS. 3, 4, 6 and 7 illustrate an embodiment of the invention.

According to the invention, the wear-resistant covering 36 of thelateral edge 22 located on the side of the pressure side 16 a of theblade 16 extends on a wall 40 a of a first ridge 40 which is locatedbetween the lips 31, 32, and on a wall 42 a of a second ridge 42 whichextends at least partly into the lip 31. The ridges 40, 42 are anintegral part of the platform 20. As can be seen in FIG. 3 , the wall 42a extends over approximately 20-50% of the height of the lip 31,measured along the stacking axis X.

The first ridge 40 is substantially straight and has a downstream endconnected to a boss 44 projecting on the external face of the platform20. This boss has a general vane profile shape and forms an extension ofthe blade 16 radially towards the outside of the platform 20.

The second ridge 42 is substantially straight and has its downstream endconnected to the upstream end of the first ridge 40. This second ridge42 is inclined with respect to the first ridge 40 in a directionsubstantially parallel to a transverse axis Z of elongation of the lip31. In other words, the second ridge 42 is substantially parallel to thelip 31 and the first ridge 40 is inclined with respect to the lip 31 andthe second ridge 42.

FIG. 7 is a cross-sectional view of the vane, with the cutting planepassing substantially through the ridges 40, 42 and the boss 44, andbeing substantially parallel to the plane of the platform 20. FIG. 7shows the thicknesses E1, E2 of the ridges 40, 42 as well as their angleof inclination a, which is for example between 120 and 150°. In otherwords, the second ridge 42 forms a substantially zero angle with the lip31 or the axis Z, and the first ridge 40 is inclined with respect to thelip 31 or the axis Z by an angle of between 30 and 60°.

This angle α is also visible in FIG. 6 which shows the ridges 40, 42inclined with respect to each other, as opposed to FIG. 5 which showsaligned ridges. In the latter case, and as explained above, the ridge 42may extend beyond the lip and the wear-resistant covering it bears maywiden the groove 46 formed in the abradable covering surrounding thevane, due to the rotation of the disc bearing this vane.

The groove 46 is partially represented here by a hatched area, thedimensions of which depend on the maximum dimensions of the lip 31. Inthe example shown, the lip 31 comprises a longitudinal end on the sideof the pressure side 16 a, in which the ridge 42 extends, and anopposite longitudinal end on the side of the suction side of the blade.The latter end is thickened in a direction perpendicular to the axis ofelongation of the lip and has a general shape known as elephant's foot.This thickened end defines the greatest thickness of the lip and thusthe thickness of the groove 46. This groove is annular and thereforeintended to extend all around the wheel bearing the vane.

In the example shown, the ridges 40, 42 define between them and with alug 48 present on the wall 40 a of the ridge 40, a first recess 50intended to receive the wear-resistant covering 36.

On the side of the suction side of the blade 16, the wear-resistantcovering is located on a wall 52 a of a third ridge 52 which has ageneral orientation substantially parallel to the ridge 40. The ridge 52has a thickness of E3. The ridge 52 defines, with two lugs 54, 56present at opposite ends of the wall 52 a, a second recess 58 intendedto receive the wear-resistant covering 36.

The thickness of a ridge is measured in a direction substantiallyperpendicular to a surface forming the ridge or to a longitudinal medianplane or an axis of elongation of the ridge. The thickness of the ridge42 can be measured in a direction substantially perpendicular to theaxis Z. The axes of elongation of the ridges 40, 42 and 52 are referredto as 40 b, 42 b and 52 b respectively in FIG. 7 .

The thicknesses E1, E2 and E3, for example, are between 1 and 3 mm. Thethickness E2 of the ridge 42 is preferably less than the thickness E1 ofthe ridge 40. For example, the thickness E1 is about 2 mm and thethickness E2 is about 1.5 mm. The thickness E3 is preferably similar tothe thickness E1, and is for example about 2 mm. These thicknessesensure good mechanical strength and prevent the formation of cracks whendepositing the stellite.

The vane can be produced in the following way. First of all, it is maderough from the metal casting. The recesses 50, 58 are then filled withthe wear-resistant coverings 36, e.g. by depositing the molten Stellite®material, which are located on the walls of the ridges. The vane canthen undergo a machining operation to set it to the desired dimensions.During this last operation, the coverings 36 can be machined, as well asthe lugs and ridges which delimit the recesses for receiving thesecoverings.

The invention claimed is:
 1. A rotor vane for an aircraft turbomachine,the rotor vane having an axis of rotation and a stacking axis andcomprising a blade extending between an internal platform and anexternal platform bearing at least one projecting lip, the bladecomprising a pressure side and a suction side and the external platformcomprising a pressure side lateral edge and a suction side lateral edgelocated on the pressure side and the suction side respectively, and eachof the pressure side lateral edge and the suction side lateral edgeconfigured to cooperate in a form-fitting manner with complementarylateral edges of adjacent vanes, each of the pressure side lateral edgeand the suction side lateral edge comprising a wear-resistant covering,wherein the wear-resistant covering of the pressure side lateral edgeextends over one first wall of a rectilinear first ridge, and over onesecond wall of a second ridge extending at least partially in the atleast one projecting lip, the wall of the second ridge being inclinedrelative to the rectilinear first ridge in a direction parallel to atransverse axis of elongation of the at least one projecting lip, andthe wall of the second ridge extending between 20 to a maximum of 50% ofa height of the at least one projecting lip in which the second ridgeextends, measured along the stacking axis.
 2. The rotor vane accordingto claim 1, wherein the rectilinear first ridge has a thickness E1 of 2mm.
 3. The rotor vane according to claim 2, wherein the second ridge hasa thickness E2 less than the thickness E1.
 4. The rotor vane accordingto claim 2, wherein the wear-resistant covering of the lateral edgelocated on a side of the suction side extends over a third wall of athird ridge, the third ridge having a thickness E3 of 2 mm.
 5. The rotorvane according to claim 1, wherein the at least one projecting lipcomprises two opposite longitudinal ends, one of which comprises atleast partially the second wall of the second ridge, and one other ofwhich comprises an excess thickness in a direction perpendicular to thetransverse axis of elongation.
 6. The rotor vane according to claim 1,wherein the at least one projecting lip is inclined with respect to aplane perpendicular to the axis of rotation.
 7. The rotor vane accordingto claim 1, wherein the second ridge has a first end connected to oneend of the rectilinear first ridge and a second free end located at thepressure side lateral edge.
 8. A rotor wheel for an aircraftturbomachine, comprising a disc carrying at a periphery an annular rowof rotor vanes according to claim 1.